From f4a6095a08c08bc6539d48dee932cee887a9b54c Mon Sep 17 00:00:00 2001
From: Chemaclass <chemaclass@outlook.es>
Date: Tue, 16 Jun 2026 08:46:34 +0200
Subject: [PATCH 1/2] fix(coverage): use builtin printf so printf spy cannot
 drop coverage data

Spying or mocking the printf builtin in a test shadowed the bare printf
calls in coverage flush_buffer, redirecting the buffered coverage write
to the spy instead of the data file. All coverage for that test was
silently lost. Flush with `builtin printf` to bypass the shadow.

Closes #724
---
 CHANGELOG.md                     |  1 +
 src/coverage.sh                  |  8 +++++---
 tests/unit/coverage_core_test.sh | 30 ++++++++++++++++++++++++++++++
 3 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 76bd7dcb..e8de0bab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 ### Fixed
 - Coverage report now counts backslash line-continuation lines as covered: a multi-line statement's hit is propagated forward across its continuation chain, so the lines after a trailing `\` are no longer reported as uncovered (#722)
+- Spying or mocking the `printf` builtin no longer breaks coverage collection: the coverage buffer is now flushed with `builtin printf`, so a test double can no longer shadow the write and silently drop all coverage data for that test (#724)
 
 ### Changed
 - Documentation and project URLs now point to the new primary domain `bashunit.com` (old `bashunit.typeddevs.com` continues to work as a redirect)
diff --git a/src/coverage.sh b/src/coverage.sh
index 4807aa09..097766ce 100644
--- a/src/coverage.sh
+++ b/src/coverage.sh
@@ -330,11 +330,13 @@ function bashunit::coverage::flush_buffer() {
     test_hits_file="${_BASHUNIT_COVERAGE_TEST_HITS_FILE}.$$"
   fi
 
-  # Write buffered data in a single I/O operation
-  printf '%s' "$_BASHUNIT_COVERAGE_BUFFER" >>"$data_file"
+  # Write buffered data in a single I/O operation.
+  # Use `builtin printf` so a user test spying/mocking the printf builtin
+  # cannot shadow the coverage write and silently drop data (see issue #724).
+  builtin printf '%s' "$_BASHUNIT_COVERAGE_BUFFER" >>"$data_file"
 
   if [ -n "$_BASHUNIT_COVERAGE_HITS_BUFFER" ]; then
-    printf '%s' "$_BASHUNIT_COVERAGE_HITS_BUFFER" >>"$test_hits_file"
+    builtin printf '%s' "$_BASHUNIT_COVERAGE_HITS_BUFFER" >>"$test_hits_file"
   fi
 
   # Reset buffer
diff --git a/tests/unit/coverage_core_test.sh b/tests/unit/coverage_core_test.sh
index fdf0fc34..1351d66e 100644
--- a/tests/unit/coverage_core_test.sh
+++ b/tests/unit/coverage_core_test.sh
@@ -268,6 +268,36 @@ function test_coverage_record_line_writes_to_file() {
   assert_contains "$test_file:20" "$content"
 }
 
+function test_coverage_flush_buffer_writes_even_when_printf_is_spied() {
+  BASHUNIT_COVERAGE="true"
+  BASHUNIT_COVERAGE_PATHS="/"
+  BASHUNIT_COVERAGE_EXCLUDE=""
+  bashunit::coverage::init
+
+  local test_file="/some/path/script.sh"
+  bashunit::coverage::record_line "$test_file" "10"
+  bashunit::coverage::record_line "$test_file" "20"
+
+  # A user test spying on the printf builtin must not shadow the coverage
+  # internals: buffered data must still be flushed to disk (see issue #724).
+  bashunit::spy printf
+
+  bashunit::coverage::flush_buffer
+
+  bashunit::unmock printf
+
+  local data_file="$_BASHUNIT_COVERAGE_DATA_FILE"
+  if bashunit::parallel::is_enabled; then
+    data_file="${_BASHUNIT_COVERAGE_DATA_FILE}.$$"
+  fi
+
+  local content
+  content=$(cat "$data_file")
+
+  assert_contains "$test_file:10" "$content"
+  assert_contains "$test_file:20" "$content"
+}
+
 function test_coverage_cleanup_removes_temp_files() {
   BASHUNIT_COVERAGE="true"
   bashunit::coverage::init

From 15e30ae88ff58a22a8baf6f6deef80e1864d5de6 Mon Sep 17 00:00:00 2001
From: Chemaclass <chemaclass@outlook.es>
Date: Tue, 16 Jun 2026 08:49:42 +0200
Subject: [PATCH 2/2] test(coverage): tidy printf-spy regression test

---
 tests/unit/coverage_core_test.sh | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tests/unit/coverage_core_test.sh b/tests/unit/coverage_core_test.sh
index 1351d66e..5af83d72 100644
--- a/tests/unit/coverage_core_test.sh
+++ b/tests/unit/coverage_core_test.sh
@@ -278,12 +278,9 @@ function test_coverage_flush_buffer_writes_even_when_printf_is_spied() {
   bashunit::coverage::record_line "$test_file" "10"
   bashunit::coverage::record_line "$test_file" "20"
 
-  # A user test spying on the printf builtin must not shadow the coverage
-  # internals: buffered data must still be flushed to disk (see issue #724).
+  # Spying printf must not shadow the coverage write (issue #724)
   bashunit::spy printf
-
   bashunit::coverage::flush_buffer
-
   bashunit::unmock printf
 
   local data_file="$_BASHUNIT_COVERAGE_DATA_FILE"